Final answer:
Breathing is easier at sea level due to higher atmospheric pressure, which facilitates oxygen uptake and carbon dioxide release. At higher elevations, reduced pressure results in lower hemoglobin saturation with oxygen, making it difficult to breathe and sometimes leading to altitude sickness. Acclimatization and physiological adaptations can help the body cope with lower oxygen levels at high altitudes.
Step-by-step explanation:
The reason it is easier to breathe at sea level compared to higher altitudes relates to atmospheric pressure and the partial pressure of oxygen. At sea level, atmospheric pressure is higher, allowing for a greater exchange of gases—specifically, more efficient uptake of oxygen and release of carbon dioxide. At higher altitudes, the reduced atmospheric pressure leads to lower oxygen saturation in hemoglobin. This means that even though the proportion of oxygen in the atmosphere remains constant at 21 percent, its partial pressure drops, leading to difficulties in providing the body with adequate oxygen.
Mountain climbers often experience acute mountain sickness (AMS) because the lower barometric pressure affects the body's oxygen intake. Those who ascend to high altitudes need time to acclimatize, as the body undergoes physiological changes, such as producing more hemoglobin, to cope with the reduced oxygen levels. However, during physical exertion at high altitudes, the body's low oxygen reserve can lead to symptoms of AMS.
To counteract low oxygen availability in the blood caused by reduced partial pressure at high elevations, adaptations include increased release of oxygen from hemoglobin to the tissues and production of more BPG by erythrocytes, which facilitates this release. Additionally, people at high altitudes might experience increased urination, which helps concentrate erythrocytes in the blood and improve tissue oxygenation.